JSFiddle - React, Tailwind, and code Playground

HTML

<div id="content_post">
    <p>If  an American doctor of the late 19th century stepped into a time warp  and emerged in 2010, he would be shocked by the multitude of  pharmaceuticals that today's physicians use. But as he pondered this  array (and wondered, as I do, whether most are really necessary), he  would soon notice an equally surprising omission, and exclaim, "Where's  my Cannabis indica?"</p>
                                        <p>No  wonder -- the poor fellow would feel nearly helpless without it. In his  day, labor pains, asthma, nervous disorders and even colicky babies  were treated with a fluid extract of Cannabis indica, also known as  "Indian hemp." (Cannabis is generally seen as having three species --  sativa, indica and ruderalis -- but crossbreeding is common, especially  between sativa and indica.) At least 100 scientific papers published in  the 19th century backed up such uses.</p>                                        <p>Then  the Marihuana Tax Act of 1937 made possession or transfer of Cannabis  illegal in the U.S. except for certain medical and industrial uses,  which were heavily taxed. The legislation began a long process of making  Cannabis use illegal altogether. Many historians have examined this  sorry chapter in American legislative history, and the dubious evidence  for Cannabis addiction and violent behavior used to secure the bill's  passage. "Under the Influence: The Disinformation Guide to Drugs" by  Preston Peet makes a persuasive case that the Act's real purpose was to  quash the hemp industry, making synthetic fibers more valuable for  industrialists who owned the patents.</p>                                        <p>Meanwhile,  as a medical doctor and botanist, my aim has always been to filter out  the cultural noise surrounding the genus Cannabis and see it  dispassionately: as a plant with bioactivity in human beings that may  have therapeutic value. From this perspective, what can it offer us?</p>
               ...

CSS

body {
    margin-top: 60px;
}
#content_post {
    float: left;
    overflow: hidden;
    height: 200px;
    width: 300px;
}
#scrover-scroller-element {
    float: right;
    height: 100px;
    width: 15px;
    background-color: #ccc;
}
#scrover-scroller-knob {
    height: 15px;
    width: 15px;
    background-color: #000;
}

JavaScript

var ContentPost = document.id('content_post');
var Steps = ContentPost.getScrollSize().y - ContentPost.getStyle('height').toInt();
    
    if(Steps == 0){
            // Hide scrollbar!
    }
    
    Slider = new Slider('scrover-scroller-element', 'scrover-scroller-knob', {
            mode: 'vertical',
            steps: Steps,
            wheel: true,
    }).addEvent('change', function(position){
            ContentPost.scrollTo(0, position);
    });
    
    Slider.element.addEvent('mousewheel', function(event){
        var mode = (this.options.mode == 'horizontal') ? (event.wheel < 0) : (event.wheel > 0);
        this.set(this.step + (mode ? -1 : 1) * this.stepSize * Math.abs(event.wheel * 20));
        event.preventDefault();
    }.bind(Slider));